You can get a negative amortization loan, where your balance goes up.

NPR: Mortgage Crisis Spreads To Conventional Loans

The credit boom was created by initially low adjustable rate mortgages, interest-only or negative amortization loans, and an appreciating real estate market that allowed homeowners to extract equity to help make mortgage payments.

FORBES: From Subprime To The Ridiculous

But as PIK loans written in 2006 and 2007 begin to term out over the next few years, investors in these instruments may suffer the same fate as investors in negative amortization subprime loans.

FORBES: Are Floating Rate Funds The Wrong Answer To Rising Rates?

For example, following lengthy comment periods, in 2006, the federal banking supervisors issued formal guidance on underwriting and managing the risks of nontraditional mortgages, such as interest-only and negative amortization mortgages, as well as guidance warning banks against excessive concentrations in commercial real estate lending.

FORBES: Transcript

They, among other things, cannot have certain risky features like negative-amortization, where the amount owed actually increases for some period because the borrower does not even pay the interest and the unpaid interest gets added to the amount borrowed.

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